Maxwell was outrighted to Triple-A Nashville on Thursday, Susan Slusser of the San Francisco Chronicle reports.
Maxwell will report to the Sounds after passing through waivers unclaimed. The 27-year-old backstop has spent the majority of the season in the minors, slashing .219/.300/.281 across 51 games with Triple-A Nashville. He owns a career .240/.314/.347 line across 127 major-league games.